A printer according to the preamble is previously known from, for example, SE B 8401146-9. The document is fed in through an input/output opening along a transport path. In the transport path and in connection with the print bar of the printer there is an interaction region in which the head cooperates with the document. On both sides of the interaction region there are a drive roll and a pressure roll to drive the document. Inside the inner drive roll and pressure roll is a guide rail to guide the document. In the above mentioned publication it is furthermore indicated that the printing head of the apparatus may be constructed to print at several stations. In what way this is carried out is not shown but may, for example, be obtained by rotating the head in correspondence with the subject matter shown in SE B 7604415-5 which correspond to British Patent GB 1527634. In this case the head is rotatable between two print stations around a shaft parallel to the movement direction of the head.
A drawback in the prior art printer is that the fed document is not guided in the interaction region above the print bar or in its vicinity. Documents which are particularly difficult to handle, such as for example bank books having spreading paper sheets and fed from a side, easily deviate from the transport path and may be damaged or damage the apparatus and at the same time recording or reading is not possible during the input and output process. The operator is forced to make new attempts with relatively small chances to succeed.